1. Field of the Invention
The present invention relates to a disc cartridge, and more specifically to a cleaning mechanism in a disc cartridge case for cleaning a recording disc.
2. Discussion of the Related Art
In a disc cartridge containing a recording disc, such as a so called floppy disc rotatably mounted in a cartridge case, there have been proposed various kinds of cleaning mechanisms for cleaning the floppy disc. FIG. 1 shows a typical conventional disc cartridge of the above kind, wherein an outer case 3 is formed by combining a top half 1 and a bottom half 2 each made of a hard plastic resin material. Head insertion windows 1a and 2a are defined in the top half 1 and bottom half 2 respectively and a drive hole 2b is defined at the center portion of the bottom half 2. A floppy disc 4 is accommodated in the space between the top and bottom halves 1 and 2 with a hub 5 of the floppy disc 4 exposed outside of the outer case 3 through the drive hole 2b so that the hub 5 and the floppy disc 4 can be rotated by a disc drive device (not shown).
In the disc cartridge mentioned above, a cleaning mechanism is usually provided in such a manner as described hereinafter.
A plurality of short parallel ribs 7 are formed on an inner surface of the top half 1 so as to face with a resilient plate 8a of a resilient member 8 hinged on the inner face of the bottom half 2 in a canti-lever manner. An upper cleaning sheet 9 and lower cleaning sheet 10 made of non woven sheet having a cleaning effect, with a generally C shape, are respectively provided on the inner surfaces of the top half 1 and bottom half 2 with the entire area or partial area bonded to the respective halves by an adhesive agent or thermal bonding agent. The disc is disposed between the upper sheet 9 and lower sheet 10 in a sandwich manner, as shown in FIG. 2, so as to press the cleaning sheets 9, 10 and the disc 4 by the resilient plate 8a toward the ribs 7. By this arrangement, both of the recording surfaces of the disc 4 can be cleaned by the cleaning sheet when the disc is rotated.
However, in the conventional cleaning mechanism mentioned above, the disc 4 is always subjected to pressure therefore, during a long time storage of the disc cartridge, the disc 4 may be deformed more or less partially at the position where the resilient plate 8a presses against the disc. In addition, foreign matter which was once caught by the cleaning sheets may be undesirably transferred to the disc 4, whereby there occurs an output fluctuation. In order to avoid the problems mentioned above, the pressure of the resilient member 8 against the cleaning sheets must be decreased, thereby resulting in a reduction in the cleaning effect. In addition, in case the top half 1 is bent, the level at which the disc 4 contacts the ribs i.e., the level of the rotational surface of the disc 4, may be displaced and error occurs in the rotational level of the disc 4.
Another conventional cleaning mechanism is shown in FIGS. 3 to 8, wherein the upper sheet 9 and lower sheet 10 are associated respectively with both halves 1 and 2, similar to the cleaning sheets shown in FIG. 1. There is provided a projection 11 on the inner surface of the top half 1 opposite the position of the head insertion window 1a of the top half 1. A through hole 12 of a square shape is defined in one corner of the bottom half 2 corresponding to the projection 11 so that a cleaning piece 13 of a generally square shape can be inserted into and removed from the disc cartridge through the through hole 12. As shown in FIGS. 4 to 6, a continuous rib 14 surrounding the hole 12 is formed on the inner face of the bottom half 2 with a receiving flange 15 formed at the inner peripheries of the rib 14 so as to receive stepped peripheral edges 13a of the cleaning piece 13 of a generally T shape in cross section on the flange 15, thereby preventing the cleaning piece 13 from being removed from the outer case 3. The disc 4 is kept between the upper and lower sheets 9 and 10 in a similar manner as mentioned in the first example.
In the second example, when the cartridge is not in use, as shown in FIG. 7, the disc 4 kept between the projection 11 and cleaning piece 13 can slightly contact either with the upper sheet 9 and lower sheet 10 at a minimal pressure. However, when the cartridge is used, as shown in FIG. 8, upon mounting of the cartridge on the disc drive device 20, a pressing member 16 provided by the disc drive device 20, pushes the cleaning piece 13 upward. The disc 4 is pressed toward the projection 11 via the upper and lower sheets 9 and 10, whereby the disc 4 can be cleaned.
The cleaning mechanism shown in the second example has a good cleaning effect and the foreign matter once caught by the upper and lower sheets 9 and 10 can not be transferred again to the disc 4. However, the drawback whereby the rotation level of the disc 4 may be changed if the top half 1 is bent is not eliminated.
As mentioned above, in the conventional cleaning mechanism, since the parallel ribs 7 in the first example and the projection 11 in the second example are formed integral with the top half 1, contact of the recording and reproducing head of the disc drive device to the recording surface of the disc 4 i.e., so called "head touch", is bad due to the change of the level of the disc. Besides, in order to realize the best cleaning effect by the upper and lower cleaning sheets 9 and 10, it is best to provide the cleaning mechanism, including the ribs 7 or projection 11, at the up stream side near the head insertion windows 1a and 2a. However, by this arrangement, the undesirable effect of a change, a the rotation level of the disc 4, due to the bending of the top half 1, develops. Accordingly, in the conventional disc cartridge, the cleaning mechanism is provided at a position apart from the head insertion windows 1a and 2a, thus the disc 4 will contact the magnetic head after cleaning, so that foreign matter may collect on the cleaned sheets between the cleaning portion and the head insertion window and the cleaning effect is decreased.